Traditionally, containers for shipping temperature sensitive products have generally included conventional cardboard shipping cartons having an insulating material therein, such as expanded polystyrene (EPS). EPS is a relatively inexpensive insulating material that may be easily formed into a desired shape, and has acceptable thermal insulating properties for many shipping needs.
Containers including EPS are often provided in a modular form. Individual panels of EPS insulation, possibly wrapped in foil or the like, are preformed using conventional methods, typically with beveled edges. The panels are then inserted into a conventional shipping carton against each wall to create an insulated cavity within the carton, the beveled edges of adjacent panels forming seams along the corners of the carton. A product is placed in the cavity and a plug, such as a thick polyether or polyester foam pad, is placed over the top of the product before the carton is closed and prepared for shipping. In many cases, a coolant, such as packaged ice, gel packs, or loose dry ice, is placed around the product in the cavity to refrigerate the product during shipping.
Alternatively, an insulated body may be injection molded from expanded polystyrene, forming a cavity therein and having an open top to access the cavity. A product is placed in the cavity, typically along with coolant, and a cover is placed over the open end, such as the foam plug described above or a cover formed from EPS.
For shipping particularly sensitive products, such as certain medical or pharmaceutical products, rigid polyurethane containers are often used, as polyurethane has thermal properties generally superior to EPS. Typically, a cardboard carton is provided having a box liner therein, defining a desired insulation space between the liner and the carton. Polyurethane foam is injected into the insulation space, substantially filling the space and generally adhering to the carton and the liner. The interior of the box liner provides a cavity into which a product and coolant may be placed. A foam plug may be placed over the product, or a lid may be formed from polyurethane, typically having a flat or possibly an inverted top-hat shape.
Conventional insulated shipping containers have many problems, particularly when shipping temperature sensitive products for extended periods of time, such as when products are shipped internationally. These containers, especially the modular liner systems, often include a number of seams in the insulating material through which air can enter and heat the cavity in the carton. In addition, the cavity often includes air spaces around the product and coolant which can facilitate convection, especially if the insulating material includes leaking seams. These conditions may accelerate the melting of the coolant, consequently shortening the time that the container can maintain a refrigerated condition. In addition, the cover or plug may be formed from a different material, such as polyester foam, which may have a thermal resistance substantially lower than the body itself, and thus may compromise the performance of the container.
Furthermore, the product and coolant are typically placed together within the cavity in the carton, which may have several adverse effects. When shipping certain products, it may be desired to refrigerate but not freeze the product. Placing a coolant, such as loose blocks of dry ice, into the cavity against the product may inadvertently freeze and damage the product. Even if held away from the product, the coolant may shift in the cavity during shipping, especially as it melts and shrinks in size, inadvertently contacting the product. In addition, melted coolant may leak from its container, possibly creating a mess within the cavity or even contaminating the product being shipped.
Finally, polyurethane containers may also create a disposal problem. When polyurethane is injected into a carton, it generally adheres substantially to the walls of the carton. Thus, the cardboard and insulation components may have to be disposed of together, preventing recycling of the container.
Accordingly, there is a need for an improved shipping container to maintain temperature sensitive material in a refrigerated condition for an extended period of time.